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Encyclopedia > Vacuum tube
Structure of a vacuum tube diode
Structure of a vacuum tube diode
Structure of a vacuum tube triode
Structure of a vacuum tube triode
An old NEC vacuum tube
An old NEC vacuum tube

In electronics, a vacuum tube, electron tube (in North America), thermionic valve, or just valve (elsewhere, especially in Britain) is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space. Some special function vacuum tubes are filled with low-pressure gas: these are so-called soft valves (or tubes), as distinct from the hard vacuum type which have the internal gas pressure reduced as far as possible. Almost all depend on the thermal emission of electrons, hence thermionic. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... For other uses, see NEC (disambiguation). ... Surface mount electronic components Electronics is the study of the flow of charge through various materials and devices such as semiconductors, resistors, inductors, capacitors, nano-structures and vacuum tubes. ... For the British rock band of the same name, see Amplifier (band). ... Electrical switches. ... Electricity (from New Latin Ä“lectricus, amberlike) is a general term for a variety of phenomena resulting from the presence and flow of electric charge. ... In information theory, a signal is the sequence of states of a communications channel that encodes a message. ... For other uses, see Electron (disambiguation). ... Look up Vacuum in Wiktionary, the free dictionary. ... Closeup of the filament on a low pressure mercury gas discharge lamp showing white thermionic emission mix coating on the central portion of the coil. ...


Vacuum tubes were critical to the development of electronics technology, which drove the expansion and commercialization of radio broadcasting, television, radar, sound reproduction, large telephone networks, analog and digital computers, and industrial process control. Some of these applications pre-dated electronics, but it was the vacuum tube that made them widespread and practical. For other uses, see Radar (disambiguation). ... High-end audio is a term used to describe equipment that is purported by the manufacturers to be the best, regardless of the price. ... For other uses, see Telephone (disambiguation). ... This article is about the machine. ... Process control is a statistics and engineering discipline that deals with architectures, mechanisms, and algorithms for controlling the output of a specific process. ...


For most purposes, the vacuum tube has been replaced by solid-state semiconductor devices such as transistors and solid-state diodes. Solid-state devices last much longer, are smaller, more efficient, more reliable, and cheaper than equivalent vacuum tube devices. However, tubes are still used in specialized applications: for engineering reasons, as in high-power radio frequency transmitters; or for their aesthetic appeal, as in audio amplification. Cathode ray tubes are still used as display devices in television sets, video monitors, and oscilloscopes, although they are being replaced by LCDs and other flat-panel displays. A specialized form of the electron tube, the magnetron, is the source of microwave energy in microwave ovens and some radar systems. In electronics, solid state circuits are those that do not contain vacuum tubes. ... Semiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium and gallium arsenide. ... Assorted discrete transistors A transistor is a semiconductor device, commonly used as an amplifier or an electrically controlled switch. ... Closeup of the image below, showing the square shaped semiconductor crystal various semiconductor diodes, below a bridge rectifier Structure of a vacuum tube diode In electronics, a diode is a two-terminal component, almost always one that has electrical properties which vary depending on the direction of flow of charge... This article uses the term tube amplifier, also known as a valve amplifier. ... Cathode ray tube employing electromagnetic focus and deflection Cutaway rendering of a color CRT: 1. ... Nineteen inch (48 cm) CRT computer monitor A computer display, monitor or screen is a computer peripheral device capable of showing still or moving images generated by a computer and processed by a graphics card. ... Illustration showing the interior of a cathode-ray tube for use in an oscilloscope. ... LCD redirects here. ... Flat panel displays encompass a growing number of technologies enabling video displays that are lighter and much thinner than traditional television and video displays that use cathode ray tubes, and are usually less than 4 inches (100 mm) thick. ... A cavity magnetron is a high-powered vacuum tube that generates coherent microwaves. ... Microwave oven A microwave oven, or microwave, is a kitchen appliance employing microwave radiation primarily to cook or heat food. ...

Contents

Explanation

A vacuum tube consists of electrodes in a vacuum in a (usually tubular) insulating heat-resistant envelope. Many tubes have glass envelopes, though some types such as power tubes may have ceramic or metal envelopes. The electrodes are attached to leads which pass through the envelope via an airtight seal. On most tubes, the leads are designed to plug into a tube socket for easy replacement. For other uses, see Electrode (disambiguation). ... Look up Vacuum in Wiktionary, the free dictionary. ... Left to right: octal (top and bottom view), loctal, and miniature (top and side view) sockets. ...


The simplest vacuum tubes resemble incandescent light bulbs in that they have a filament sealed in a glass envelope which has been evacuated of all air. When hot, the filament releases electrons into the vacuum: a process called thermionic emission. The resulting negatively-charged cloud of electrons is called a space charge. These electrons will be drawn to a metal plate inside the envelope, if the plate (also called the anode) is positively charged relative to the filament (or cathode). The result is a flow of electrons from filament to plate. This cannot work in the reverse direction because the plate is not heated and does not emit electrons. This very simple example described can thus be seen to operate as a diode: a device that conducts current only in one direction. The vacuum tube diode conducts conventional current from plate (anode) to the filament (cathode); this is the opposite direction to the flow of electrons (called electron current). Molten glassy material glows orange with incandescence in a vitrification experiment. ... The incandescent light bulb or incandescent lamp is a source of artificial light that works by incandescence, (a general term for heat-driven light emissions which includes the simple case of black body radiation). ... An electrical filament is a thread of metal, usually tungsten, which is used to convert electricity into light in incandescent light bulbs (as developed in 1878 by Joseph Wilson Swan, among others), and into heat in vacuum tube devices. ... For other uses, see Electron (disambiguation). ... Closeup of the filament on a low pressure mercury gas discharge lamp showing white thermionic emission mix coating on the central portion of the coil. ... Space charge is the electrical current that results when a metal object is heated to incandescence in a vacuum. ... Diagram of a zinc anode in a galvanic cell. ... Hot cathode is also a name for a hot filament ionization gauge, a vacuum measuring device. ... Closeup of the image below, showing the square shaped semiconductor crystal various semiconductor diodes, below a bridge rectifier Structure of a vacuum tube diode In electronics, a diode is a two-terminal component, almost always one that has electrical properties which vary depending on the direction of flow of charge... In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ...


Vacuum tubes operate primarily on the function of the heat gradient difference between the hot cathode and the cold anode. Because of this operating requirement, vacuum tubes are inherently power-inefficient; enclosing the tube within a heat-retaining envelope of insulation would allow the entire tube to reach the same temperature, resulting in electron emission from the anode that would counter the normal one-way current flow. Because the tube requires a vacuum to operate, convection cooling of the anode is typically not possible. Instead anode cooling occurs primarily through black-body radiation and conduction of heat to the outer glass envelope via the anode mounting frame. Cold cathode tubes do exist but are used primarily in lighting systems, where unidirectional power regulation is not the functional purpose of the tube.[citations needed] As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ... This article is about light sources and indicators. ...


The vacuum tube is a voltage-controlled device, with the relationship between the input and output circuits determined by a transconductance function. The solid-state device most closely analogous to the vacuum tube is the JFET, although the vacuum tube typically operates at far higher voltage (and power) levels than the JFET. Transconductance, also known as mutual conductance, is a property of certain electronic components. ... Electric current flow from source to drain in a p-channel JFET is restricted when a voltage is applied to the gate. ...


History of development

Inside of a vacuum tube with plate cut open.
Inside of a vacuum tube with plate cut open.

The 19th century saw increasing research with evacuated tubes, such as the Geissler and Crookes tubes. Scientists who experimented with such tubes included Eugen Goldstein, Nikola Tesla, Johann Wilhelm Hittorf, Thomas Edison, and many others. These tubes were mostly for specialized scientific applications, or were novelties, with the exception of the light bulb. The groundwork laid by these scientists and inventors, however, was critical to the development of vacuum tube technology. Image File history File links Download high resolution version (955x1245, 561 KB) Summary Octal-base power w:vacuum tube cut open. ... Image File history File links Download high resolution version (955x1245, 561 KB) Summary Octal-base power w:vacuum tube cut open. ... The Geissler tube is a glass tube for demonstrating the principles of electrical discharge. ... The Crookes tube is an evacuated glass cone with 3 node elements (one anode and two cathodes). ... Among the important early researchers in X-rays were Sir William Crookes, Johann Wilhelm Hittorf, Eugene Goldstein, Heinrich Hertz, Philipp Lenard, Hermann von Helmholtz, Thomas Edison, Nikola Tesla, Charles Barkla, and Wilhelm Conrad Roentgen. ... Nikola Tesla (Nih koh la TESS lah) [2](Serbian Cyrillic: ) (10 July 1856 – 7 January 1943) was an inventor, physicist, mechanical and electrical engineer. ... Johann Wilhelm Hittorf (March 27, 1824 – November 28, 1914) was a German physicist, born in Bonn, who observed tubes with energy rays extending from a negative electrode. ... Edison redirects here. ... The light bulb is one of the most significant inventions in the history of the human race, illuminating the darkness of the evening and bringing light indoors at all times in order focus on the task at hand. ...


Though the thermionic emission effect was originally reported in 1873 by Frederick Guthrie, it is Thomas Edison's 1884 investigation of the "Edison Effect" that is more often mentioned. Edison patented what he found,[1] but he did not understand the underlying physics, or the potential value of the discovery. Closeup of the filament on a low pressure mercury gas discharge lamp showing white thermionic emission mix coating on the central portion of the coil. ... Frederick Guthrie was a scientific writer and professor in London who lived from 1833 to 1886. ... Thermionic emission is the flow of electrons from a metal or metal oxide surface, caused by thermal vibrational energy overcoming the electrostatic forces holding electrons to the surface. ...


Diodes and triodes

The English physicist John Ambrose Fleming worked as an engineering consultant for technology firms, including Edison Telephone; in 1904, as a result of experiments conducted on Edison Effect bulbs imported from the USA and while working as scientific adviser to the Marconi company, he developed a device he called an "oscillation valve" (because it passes current in only one direction) or kenotron, which can also be used as part of a radio wave detector. Later known as the Fleming valve and then the diode, it allowed electrical current to flow in only one direction, enabling the rectification of alternating current. Sir John Ambrose Fleming (November 29, 1849 - April 18, 1945) was an English electrical engineer and physicist. ... The Marconi Company Ltd. ... Fleming valve schematic from US Patent 803,684. ... Closeup of the image below, showing the square shaped semiconductor crystal various semiconductor diodes, below a bridge rectifier Structure of a vacuum tube diode In electronics, a diode is a two-terminal component, almost always one that has electrical properties which vary depending on the direction of flow of charge... In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ... A rectifier is an electrical device that converts alternating current to rectified direct current, a process known as rectification. ...


In 1906 Robert von Lieben filed[2] for a three electrode amplifying vacuum tube. His invention included also a beam focusing electromagnet. Robert von Lieben (September 5, 1878 in Vienna – February 20, 1913 in Vienna) was a notable Austrian physicist. ...


In 1907 Lee De Forest placed a bent wire serving as a screen, later known as the "grid" electrode, between the filament and plate electrode. As the voltage applied to the grid was varied from negative to positive, the number of electrons flowing from the filament to the plate would vary accordingly. Thus the grid was said to electrostatically "control" the plate current. The resulting three-electrode device was therefore an excellent and very sensitive amplifier of voltages. DeForest called his invention the "Audion". In 1907, DeForest filed[3] for a three-electrode version of the Audion for use in radio communications. The device is now known as the triode. De Forest's device was not strictly a vacuum tube, but clearly depended for its action on ionisation of the relatively high levels of gas remaining after evacuation. The De Forest company, in its Audion leaflets, warned against operation which might cause the vacuum to become too hard. The Finnish inventor Eric Tigerstedt significantly improved on the original triode design in 1914, while working on his sound-on-film process in Berlin, Germany. The first true vacuum triodes were the Pliotrons developed by Irving Langmuir at the General Electric research laboratory (Schenectady, New York) in 1915. Langmuir was one of the first scientists to realize that a harder vacuum would improve the amplifying behaviour of the triode. Pliotrons were closely followed by the French 'R' Type which was in widespread use by the allied military by 1916. These two types were the first true vacuum tubes. Historically, vacuum levels in production vacuum tubes typically ranged between 10 µPa to 10 nPa. Lee De Forest, (August 26, 1873 – June 30, 1961) was an American inventor with over 300 patents to his credit. ... The control grid is an electrode used in thermionic valves (vacuum tubes) used to modulate the flow of electrons in the cathode to anode or plate circuit. ... Diagram of Vacuum-Tube Diode A plate is a type of electrode that formed part of a vacuum tube. ... For the British rock band of the same name, see Amplifier (band). ... This article does not cite any references or sources. ... Simplified diagram of a triode. ... Eric Magnus Campbell Tigerstedt (August 4, 1887 – April 20, 1925) was one of the most significant inventors in Finland at the beginning of the 20th century, and has been called the Thomas Edison of Finland. He was the first person to implement a working sound-on-film technology, and in... 1902 poster advertising Gaumonts sound films, depicting an optimistically vast auditorium A sound film is a motion picture with synchronized sound, or sound technologically coupled to image, as opposed to a silent film. ... Irving Langmuir (January 31, 1881 in Brooklyn, New York - August 16, 1957 in Woods Hole, Massachusetts) was an American chemist and physicist. ... GE redirects here. ... Schenectady (pronounced ; Θkahnéhtati[1] in Tuscarora) is a city in Schenectady County, New York, United States, of which it is the county seat. ... Look up Pa, PA, pa in Wiktionary, the free dictionary. ...


The non-linear operating characteristic of the triode caused early tube audio amplifiers to exhibit harmonic distortions at low volumes. This is not to be confused with the overdrive that tube amplifiers exhibit at high volume levels (known as the tube sound). To remedy the low-volume distortion problem, engineers plotted curves of the applied grid voltage and resulting plate currents, and discovered that there was a range of relatively linear operation. In order to use this range, a negative voltage had to be applied to the grid to place the tube in the "middle" of the linear area with no signal applied. This was called the idle condition, and the plate current at this point the "idle current". Today this current would be called the quiescent or standing current. The controlling voltage was superimposed onto this fixed voltage, resulting in linear swings of plate current for both positive and negative swings of the input voltage. This concept was called grid bias. Overdrive in the field of rock music, is a term used for an electric guitar amplifier when turned up, usually deliberately, to the point where distortion (clipping) is clearly audible in the output signal. ... This article uses the term tube amplifier, also known as a valve amplifier. ... Electron tubes (or valves in British English) are electronic devices with two or more electrodes; grid bias is a term used on devices with three electrodes or more, such as triodes. ...


Batteries provided the voltages required by tubes in early radio sets. In North American terminology, the "A" batteries provided the filament voltage. Although North American terminology calls this the A battery, most of the English-speaking world knows it by a descriptive label: the LT (low-tension) supply or battery. These were often rechargeable—usually of the lead-acid type ranging from 2 to 12 volts (1-6 cells) with single, double and triple cells being most common. Because these batteries produced 2 V, 4 V or 6 V, tube heaters were designed to operate at those voltages—a scheme which continues to be followed today. In portable radios, flashlight (torch) batteries were sometimes used. For other uses, see Battery. ... In electronics, an A battery is any battery used to provide power to the filament of a vacuum tube. ... A valve-regulated, sometimes called sealed, lead acid battery Lead-acid batteries, invented in 1859 by French physicist Gaston Planté, are the oldest type of rechargeable battery. ...


The "B" batteries (in North American English) provided the plate voltage. These were generally of dry cell construction, containing many small 1.5 volt cells in series. They typically came in ratings of 22.5, 45, 67.5, 90 or 135 volts. To this day, plate voltage is referred to as B+, but only in North America. The rest of the English-speaking world calls this the HT (high-tension) supply or battery. In electronics, a B battery is any battery used to provide the plate voltage of a vacuum tube. ... A dry cell is a galvanic electrochemical cell with a pasty low-moisture electrolyte. ... Electrical circuit components can be connected together in one of two ways: series or parallel. ...


Some sets used "C" batteries (North American English) to provide grid bias, although many circuits used grid leak resistors, voltage dividers or cathode bias to provide proper tube bias. Most of the English-speaking world calls this simply the 'grid bias battery'. In electronics, a C battery is any battery used to provide bias to the control grid of a vacuum tube. ... Grid leak is an inherent operating characteristic of triodes and other vacuum tubes. ... Resistor symbols (American) Resistor symbols (Europe, IEC) Axial-lead resistors on tape. ... In electronics, a voltage divider is a simple device designed to create a voltage (Vout) which is proportional to another voltage (Vin). ... This article does not cite any references or sources. ...


Direct and indirect heating

Many innovations followed. It became common to use the filament to heat a separate electrode called the cathode, and to use this cathode as the source of electron flow in the tube rather than the filament itself. This minimized the introduction of hum when the filament was energized with alternating current. In such tubes, the filament is called a heater to distinguish it as an inactive element. City lights viewed in a motion blurred exposure. ... Software being used to design HVAC systems HVAC (pronounced either H-V-A-C or, occasionally, H-VAK) is an initialism/acronym that stands for heating, ventilation and air-conditioning. This is sometimes referred to as climate control. ...


Tetrodes and pentodes

A two-tube homemade radio from 1958. The tubes are the two columns with the dark tops. The flying leads connect to the low-voltage filament and high-voltage anode supplies.
A two-tube homemade radio from 1958. The tubes are the two columns with the dark tops. The flying leads connect to the low-voltage filament and high-voltage anode supplies.

When triodes were first used in radio transmitters and receivers, it was found that they had a tendency to oscillate due to parasitic anode-to-grid capacitance. Many circuits were developed to reduce this problem (e.g. the Neutrodyne amplifier), but proved unsatisfactory over wide ranges of frequencies. It was discovered that the addition of a second grid, located between the control grid and the plate and called a screen grid could solve these problems. A positive voltage slightly lower than the plate voltage was applied to it, and the screen grid was bypassed (for high frequencies) to ground with a capacitor. This arrangement decoupled the anode and the first grid, completely eliminating the oscillation problem. An additional side effect of this second grid is that the Miller capacitance is also reduced, which improves gain at high frequency. This two-grid tube is called a tetrode, meaning four active electrodes. Download high resolution version (600x700, 110 KB)A two-valve home-made radio from 1958. ... Download high resolution version (600x700, 110 KB)A two-valve home-made radio from 1958. ... The Neutrodyne was a particular type of Tuned Radio Frequency (TRF) radio receiver, in which the inter-electrode capacitance of the triode RF tubes are neutralised with interstage variable trim capacitors connected between the grid and plate of each RF amplifier tube. ... A grid introduced into a thermionic valve or tube to greatly reduce the capacitance between two other parts of the electrode structure. ... In electronics, the Miller effect describes the fact that a capacitance between input and output of an amplifier is multiplied by (with is the voltage gain) in a electrical circuit. ... This article does not cite any references or sources. ...

Radio transmitter high-power vacuum tube. The braided copper leads provide heater current for the cathode. The tube also has a heat sink. Dubendorf Museum of Military Aviation.
Radio transmitter high-power vacuum tube. The braided copper leads provide heater current for the cathode. The tube also has a heat sink. Dubendorf Museum of Military Aviation.

However, the tetrode has some new problems. In any tube, electrons strike the anode hard enough to knock out secondary electrons. In a triode these (less energetic) electrons cannot reach the grid or cathode, and are re-captured by the anode. But in a tetrode, they can be captured by the second grid, reducing the plate current and the amplification of the circuit. Since secondary electrons can outnumber the primary electrons, in the worst case, particularly when the plate voltage dips below the screen voltage, the plate current can actually go down with increasing plate voltage.[4] This is the "tetrode kink" (see the reference for a plot of this effect in the RCA-235 tetrode). Another consequence of this effect is that under severe overload, the current collected by the screen grid can cause it to overheat and melt, destroying the tube. Image File history File linksMetadata Download high resolution version (3264x1392, 543 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Vacuum tube Metadata This file contains additional information, probably added from the digital camera or scanner used to... Image File history File linksMetadata Download high resolution version (3264x1392, 543 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Vacuum tube Metadata This file contains additional information, probably added from the digital camera or scanner used to... Dübendorf is a suburb of Zürich in Switzerland with a population of about 22,700 (2004). ... Secondary emission is a phenomenon that occurs in electron tubes where electrons impact an electrode with sufficient energy to knock additional electrons from the surface of that electrode. ...


Again the solution was to add another grid, called a suppressor grid. This third grid was biased at either ground or cathode voltage and its negative voltage (relative to the anode) electrostatically suppressed the secondary electrons by repelling them back toward the anode. This three-grid tube is called a pentode, meaning five electrodes. A grid used in a thermionic valve (also called vacuum tube) to suppress secondary emission. ... This article does not cite any references or sources. ...


Other variations

12SA7 Pentagrid converter tube.
12SA7 Pentagrid converter tube.

Frequency conversion can be accomplished by various methods in superheterodyne receivers. Tubes with 5 grids, called pentagrid converters, were generally used, although alternatives such as using a combination of a triode with a hexode were also used. Even octodes have been used for frequency conversion. The additional grids are either control grids, with different signals applied to each one, or screen grids. In many designs a special grid acted as a second 'leaky' plate to provide a built-in oscillator, which then coupled this signal with the incoming radio signal. These signals create a single, combined effect on the plate current (and thus the signal output) of the tube circuit. The heptode, or pentagrid converter, was the most common of these. 6BE6 is an example of a heptode (note that the first number in the tube ID indicates the filament voltage). The Super Heterodyne receiver (or to give it its full name, The Supersonic Heterodyne Receiver) was invented by Edwin Armstrong in 1918. ... NOTE: This article is currently being extensively rewritten and expanded off line. ... Simplified diagram of a triode. ... NOTE: This article is currently being extensively rewritten and expanded off line. ... NOTE: This article is currently being extensively rewritten and expanded off line. ... The control grid is an electrode used in thermionic valves (vacuum tubes) used to modulate the flow of electrons in the cathode to anode or plate circuit. ... A grid introduced into a thermionic valve or tube to greatly reduce the capacitance between two other parts of the electrode structure. ... NOTE: This article is currently being extensively rewritten and expanded off line. ...


To reduce the cost and complexity of radio equipment, by 1940 it was common practice to combine more than one function, or more than one set of elements in the bulb of a single tube. The only constraint was where patents, and other licencing considerations required the use of multiple tubes. See British Valve Association This article does not cite any references or sources. ...


For example, the RCA Type 55 was a double diode triode used as a detector, automatic gain control rectifier and audio preamp in early AC powered radios. The same set of tubes often included the 53 Dual Triode Audio Output. Please wikify (format) this article or section as suggested in the Guide to layout and the Manual of Style. ... Automatic gain control (AGC) is an electronic system found in many types of devices. ... An example of a typical high-end stereo preamplifier. ...


Another early type of multi-section tube, the 6SN7, is a "dual triode" which, for most purposes, can perform the functions of two triode tubes, while taking up half as much space and costing less. 6SN7 is a dual triode vacuum tube, on an 8 pin octal base. ...

An RCA 12AX7 dual-triode tube (1947)
An RCA 12AX7 dual-triode tube (1947)

The 12AX7 is a dual high-gain triode widely used in guitar amplifiers, audio preamps, and instruments. RCA 12AX7 tube, 1948 (captioned, made photo myself of sample tube in August 2004) This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... RCA 12AX7 tube, 1948 (captioned, made photo myself of sample tube in August 2004) This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... This page is about amplifiers for musical instruments. ...


The invention of the 9-pin miniature tube base, besides allowing the 12AX7 family, also allowed many other multi section tubes, such as the 6GH8 triode pentode. Along with a host of similar tubes, the 6GH8 was quite popular in television receivers. Some color TV sets used exotic types like the 6JH8 which had two plates and beam deflection electrodes (known as 'sheet beam' tube). Vacuum tubes used like this were designed for demodulation of synchronous signals, an example of which is color demodulation for television receivers. Demodulation is the act of removing the modulation from an analog signal. ...

1960s era miniature tubes from Australia.
1960s era miniature tubes from Australia.

The desire to include many functions in one envelope resulted in the General Electric Compactron. A typical unit, the 6AG11 Compactron tube contained two triodes and two diodes, but many in the series had triple triodes. Image File history File links Minaturevacuumtube. ... Image File history File links Minaturevacuumtube. ... The Compactron is a 12-pin vacuum tube family introduced in 1961 by General Electric in Owensboro, Kentucky with the express purpose of keeping tubes in the market for a few more years during the solid state revolution. ...


An early example of multiple devices in one envelope was the Loewe 3NF. This 1920s device had 3 triodes in a single glass envelope together with all the fixed capacitors and resistors required to make a complete radio receiver. As the Loewe set had only one tubeholder, it was able to substantially undercut the competition since, in Germany, state tax was levied by the number of tubeholders. However, reliability was compromised, and production costs for the tube were much greater. The Loewe 3NF was an early attempt to combine several functions in one Electronic device. ...


Loewe were to also offer the 2NF (two tetrodes plus passive components) and the WG38 (two pentodes, a triode and the passive components).

Vacuum tubes in an Australian radio of the late 1930s
Vacuum tubes in an Australian radio of the late 1930s

The beam power tube is usually a tetrode with the addition of beam-forming electrodes, which take the place of the suppressor grid. These angled plates focus the electron stream onto certain spots on the anode which can withstand the heat generated by the impact of massive numbers of electrons, while also providing pentode behavior. The positioning of the elements in a beam power tube uses a design called "critical-distance geometry", which minimizes the "tetrode kink", plate-grid capacitance, screen-grid current, and secondary emission effects from the anode, thus increasing power conversion efficiency. The control grid and screen grid are also wound with the same pitch, or number of wires per inch. Aligning the grid wires also helps to reduce screen current, which represents wasted energy. This design helps to overcome some of the practical barriers to designing high-power, high-efficiency power tubes. 6L6 was the first popular beam power tube, introduced by RCA in 1936. Corresponding tubes in Europe were the KT66, KT77 and KT88 by GEC (the KT standing for "Kinkless Tetrode"). Image File history File linksMetadata Vacuumtuberadio. ... Image File history File linksMetadata Vacuumtuberadio. ... The problem of secondary emission in the tetrode tube (valve) was solved by Philips/Mullard with the introduction of a suppressor grid to produce the pentode construction. ... Pair of 6L6GC tubes: Left: General Electric version from 1960s Right: current manufacture from Svetlana Electron Devices, Russia 6L6 is the designator for a vacuum tube introduced by Radio Corporation of America in July 1936. ... This article is about the former RCA Corporation. ... Original M-OV version of the KT66; this is from late production KT66 is the designator for a vacuum tube introduced by Marconi-Osram Valve Co. ... KT88 vacuum tubes, or valves, are used in the power sections of tube amplifiers. ...


Variations of the 6L6 design are still widely used in guitar amplifiers, making it one of the longest lived electronic device families in history. Similar design strategies are used in the construction of large ceramic power tetrodes used in radio transmitters.


Special-purpose tubes

Some special-purpose tubes are constructed with particular gases in the envelope. For instance, voltage regulator tubes contain various inert gases such as argon, helium or neon, and take advantage of the fact that these gases will ionize at predictable voltages. The thyratron is a special-purpose tube filled with low-pressure gas or mercury, some of which vaporizes. Like other tubes, it contains a hot cathode and an anode, but also a control electrode, which behaves somewhat like the grid of a triode. When the control electrode starts conduction, the gas ionizes, and the control electrode no longer can stop current flow; the tube "latches" into conduction. Removing plate (anode) voltage lets the gas de-ionize, restoring its non-conductive state. Some thyratrons can carry relatively large currents for their physical size. One example is the miniature type 2D21, often seen in 1950s jukeboxes as control switches for relays. A cold-cathode version of the thyratron, which uses a pool of mercury for its cathode, is called an Ignitron (tm). It can switch thousands of amperes in its largest versions. Thyratrons containing hydrogen have a very consistent time delay between their turn-on pulse and full conduction, and have long been used in radar transmitters. Thyratrons behave much like silicon controlled rectifiers. Electronic symbol for Voltage regulator A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. ... Gas filled tubes are arrangements of electrodes in a gas within an insulating, temperature-resistant envelope. ... An inert gas is any gas that is not reactive under normal circumstances. ... General Name, symbol, number argon, Ar, 18 Chemical series noble gases Group, period, block 18, 3, p Appearance colorless Standard atomic weight 39. ... General Name, symbol, number helium, He, 2 Chemical series noble gases Group, period, block 18, 1, s Appearance colorless Standard atomic weight 4. ... For other uses, see Neon (disambiguation). ... This article is about the electrically charged particle. ... A thyratron is a type of gas filled tube used as a high energy electrical switch. ... A Zodiac jukebox A jukebox is a partially automated music-playing device, usually a coin-operated machine, that can play specially selected songs from self-contained media. ... Automotive style miniature relay A relay is an electrical switch that opens and closes under the control of another electrical circuit. ... A Silicon Controlled Rectifier (or semiconductor controlled rectifier) is a 4-layer solid state device that controls current flow. ...


Tubes usually have glass envelopes, but metal, fused quartz (silica), and ceramic are possible choices. The first version of the 6L6 used a metal envelope sealed with glass beads, while a glass disk fused to the metal was used in later versions. Metal and ceramic are used almost exclusively for power tubes above 2 kW dissipation. The nuvistor is a tiny tube made only of metal and ceramic. In some power tubes, the metal envelope is also the anode. 4CX800A is an external anode tube of this sort. Air is blown through an array of fins attached to the anode, thus cooling it. Power tubes using this cooling scheme are available up to 150 kW dissipation. Above that level, water or water-vapor cooling are used. The highest-power tube currently available is the Eimac 8974, a forced water-cooled power tetrode capable of dissipating 1.5 megawatts. (By comparison, the largest power transistor can only dissipate about 1 kilowatt.) A pair of 8974s is capable of producing 2 megawatts of audio power. The 8974 is used only in military and commercial radio-frequency installations. The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... This article is about ceramic materials. ... The nuvistor is a type of vacuum tube announced by RCA in 1959. ... In electronics, a vacuum tube (U.S. and Canadian English) or (thermionic) valve (outside North America) is a device generally used to amplify, or otherwise modify, a signal by controlling the movement of electrons in an evacuated space. ...


Reliability

Tube tester manufactured in 1930
Tube tester manufactured in 1930

The chief reliability problem of a tube is that the filament or cathode is slowly "poisoned" by atoms from other elements in the tube, which damage its ability to emit electrons. Trapped gases or slow gas leaks can also damage the cathode or cause plate-current runaway due to ionization of free gas molecules. Vacuum hardness and proper selection of construction materials are the major influences on tube lifetime. Depending on the material, temperature and construction, the surface material of the cathode may also diffuse onto other elements. The resistive heaters that heat the cathodes may break in a manner similar to incandescent lamp filaments, but rarely do, since they operate at much lower temperatures than lamps. The heater's failure mode, due to its positive temperature coefficient, is generally associated with the power-up period as a result of the switch-on current surge. A negative temperature coefficient device, such as a thermistor, was sometimes incorporated in the equipment heater supply to compensate. In vacuum tubes, a hot cathode is a cathode electrode which emits electrons due to thermionic emission. ... Ionization is the physical process of converting an atom or molecule into an ion by changing the difference between the number of protons and electrons. ... Look up Vacuum in Wiktionary, the free dictionary. ... The incandescent light bulb uses a glowing wire filament heated to white-hot by electrical resistance, to generate light (a process known as thermal radiation). ... NTC thermistor, bead type, insulated wires Thermistor symbol A thermistor is a type of resistor used to measure temperature changes, relying on the change in its resistance with changing temperature. ...


Another important reliability problem is caused by air leakage into the tube. Usually oxygen in the air reacts chemically with the hot filament or cathode, quickly ruining it. Designers developed tube designs that sealed reliably. This was why most tubes were constructed of glass. Metal alloys (such as Cunife and Fernico) and glasses had been developed for light bulbs that expanded and contracted in similar amounts, as temperature changed. These made it easy to construct an insulating envelope of glass, while passing connection wires through the glass to the electrodes. This article is about the chemical element and its most stable form, or dioxygen. ... Cunife is an alloy of copper (Cu), nickel (Ni) and iron (Fe). ... Fernico is an alloy of Iron (Fer), Nickel (Ni) and Cobalt (Co). ...


When a vacuum tube is overloaded or operated past its design dissipation, its anode (plate) may glow red. In consumer equipment, a glowing plate is universally a sign of an overloaded tube. However, some large transmitting tubes are designed to operate with their anodes at red, orange, or in rare cases, white heat. To meet Wikipedias quality standards, this article or section may require cleanup. ...


Vacuum

The vacuum inside the envelope must be as perfect, or "hard", as possible. Any gas atoms remaining might be ionized at operating voltages, and will conduct electricity between the elements in an uncontrolled manner. This can lead to erratic operation or even catastrophic destruction of the tube and associated circuitry. Unabsorbed free air sometimes ionizes and becomes visible as a pink-purple glow discharge between the tube elements. ... Electric glow discharge is a type of plasma formed by passing a current at 100V to several kV through a gas - usually argon or another noble gas. ...


To prevent any remaining gases from remaining in a free state in the tube, modern tubes are constructed with "getters", which are usually small, circular troughs filled with metals that oxidize quickly, with barium being the most common. While the tube envelope is being evacuated, the internal parts except the getter are heated by RF induction heating to extract any remaining gases from the metal. The tube is then sealed and the getter is heated to a high temperature, again by radio frequency induction heating. This causes the material to evaporate, absorbing/reacting with any residual gases and usually leaving a silver-colored metallic deposit on the inside of the envelope of the tube. The getter continues to absorb any gas molecules that leak into the tube during its working life. If a tube develops a crack in the envelope, this deposit turns a white color when it reacts with atmospheric oxygen. Large transmitting and specialized tubes often use more exotic getter materials, such as zirconium. Early gettered tubes used phosphorus based getters and these tubes are easily identifiable, as the phosphorus leaves a characteristic orange or rainbow deposit on the glass. The use of phosphorus was short-lived and was quickly replaced by the superior barium getters. Unlike the barium getters, the phosphorus did not absorb any further gases once it had fired. For other uses, see Gas (disambiguation). ... This article is about electronics. ... For other uses, see Barium (disambiguation). ... It has been suggested that this article or section be merged with Radio waves. ... A semiconductor induction heater with a small inductor Induction heating is the process of heating a metal object by electromagnetic induction, where eddy currents are generated within the metal and resistance leads to Joule heating of the metal. ... This article is about the chemical element and its most stable form, or dioxygen. ... General Name, Symbol, Number zirconium, Zr, 40 Chemical series transition metals Group, Period, Block 4, 5, d Appearance silvery white Standard atomic weight 91. ...

Schematic diagram of a 1948 vacuum tube radio from Poland.
Schematic diagram of a 1948 vacuum tube radio from Poland.

Image File history File links Download high-resolution version (1153x600, 159 KB) diagram of Pionier radio set (made in Poland since 1948) Source: http://oldradio. ... Image File history File links Download high-resolution version (1153x600, 159 KB) diagram of Pionier radio set (made in Poland since 1948) Source: http://oldradio. ...

Transmitting tubes

Large transmitting tubes have tungsten filaments containing a small trace of thorium. A thin layer of thorium atoms forms on the outside of the wire when heated, serving as an efficient source of electrons. The thorium slowly evaporates from the wire surface, while new thorium atoms diffuse to the surface to replace them. Such thoriated tungsten cathodes deliver lifetimes in the tens of thousands of hours. The claimed record is held by an Eimac power tetrode used in a Los Angeles radio station's transmitter, which was removed from service after 80,000 hours (~9 years) of operation. Transmitting tubes are also claimed to survive lightning strikes more often than transistor transmitters do. For RF power levels above 20 kilowatts, vacuum tubes are commonly more efficient and reliable than similar solid-state circuits. For other uses, see Tungsten (disambiguation). ... General Name, Symbol, Number thorium, Th, 90 Chemical series Actinides Group, Period, Block n/a, 7, f Appearance silvery white Standard atomic weight 232. ... diffusion (disambiguation). ...


Receiving tubes

Cathodes in small "receiving" tubes are coated with a mixture of barium oxide and strontium oxide, sometimes with addition of calcium oxide or aluminium oxide. An electric heater is inserted into the cathode sleeve, and insulated from it electrically by a coating of aluminium oxide. This complex construction causes barium and strontium atoms to diffuse to the surface of the cathode when heated to about 780 degrees Celsius, thus emitting electrons. ... Strontium Oxide SrO is formed when strontium reacts with oxygen. ... Calcium oxide (CaO), commonly known as burnt lime, lime or quicklime, is a widely used chemical compound. ... Alumina redirects here. ...


Computer vacuum tubes

See also: List of vacuum tube computers

Colossus

The Colossus computer's designer, Dr Tommy Flowers, had a theory that most of the unreliability was caused during power down and (mainly) power up. Once Colossus was built and installed, it was switched on and left switched on running from dual redundant diesel generators (the wartime mains supply being considered too unreliable). The only time it was switched off was for conversion to the Colossus Mk2 and the addition of another 500 or so tubes. Another 9 Colossus Mk2s were built, and all 10 machines ran with a surprising degree of reliability. The 10 Colossi consumed 15 kilowatts of power each, 24 hours a day, 365 days a year—nearly all of it for the tube heaters. A Colossus Mark II computer. ... Thomas (Tommy) Harold Flowers, MBE (22 December 1905 – 28 October 1998) was a British engineer. ...


Whirlwind

To meet the reliability requirements of the early digital computer Whirlwind, it was necessary to build special "computer vacuum tubes" with extended cathode life. The problem of short lifetime was traced to evaporation of silicon, used in the tungsten alloy to make the heater wire easier to draw. Elimination of the silicon from the heater wire alloy (and paying extra for more frequent replacement of the wire drawing dies) allowed production of tubes that were reliable enough for the Whirlwind project. The tubes developed for Whirlwind later found their way into the giant SAGE air-defense computer system. High-purity nickel tubing and cathode coatings free of materials that can poison emission (such as silicates and aluminium) also contribute to long cathode life. The first such "computer tube" was Sylvania's 7AK7 of 1948. By the late 1950s it was routine for special-quality small-signal tubes to last for hundreds of thousands of hours, if operated conservatively. This reliability made mid-cable amplifiers in submarine cables possible. The Whirlwind computer was developed at the Massachusetts Institute of Technology. ... Not to be confused with Silicone. ... For other uses, see Tungsten (disambiguation). ... For other uses, see Wire (disambiguation). ... For other uses of this term, see Die. ... SAGE Sector Control Room. ... For other uses, see Nickel (disambiguation). ... In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ... Aluminum redirects here. ... A cross-section of a submarine communications cable. ...


World War II

A CV4501 subminiature tube for use in a military radio set. The tube is a special quality type based on the EF72, 35 mm long and 10 mm in diameter (excluding leads).
A CV4501 subminiature tube for use in a military radio set. The tube is a special quality type based on the EF72, 35 mm long and 10 mm in diameter (excluding leads).

Near the end of World War II, to make radios more rugged, some aircraft and army radios began to integrate the tube envelopes into the radio's cast aluminium or zinc chassis. The radio became just a printed circuit with non-tube components, soldered to the chassis that contained all the tubes. Another WWII idea was to make very small and rugged glass tubes, originally for use in radio-frequency metal detectors built into artillery shells. These proximity fuzes made artillery more effective. Tiny tubes were later known as "subminiature" types. They were widely used in 1950s military and aviation electronics. Image File history File linksMetadata Download high-resolution version (2272x1704, 1183 KB) Military Quality subminiature valve. ... Image File history File linksMetadata Download high-resolution version (2272x1704, 1183 KB) Military Quality subminiature valve. ... Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... Aluminum redirects here. ... General Name, symbol, number zinc, Zn, 30 Chemical series transition metals Group, period, block 12, 4, d Appearance bluish pale gray Standard atomic weight 65. ... For other uses, see Artillery (disambiguation). ... A proximity fuze (also called a VT fuze, for variable time) is a fuze that is designed to detonate an explosive automatically when the distance to target becomes smaller than a predetermined value or when the target passes through a given plane. ...


Applications

Tubes were heavily used in the early generations of electronic devices, such as radios, televisions, and early computers such as the Colossus which used 2000 tubes, the ENIAC which used nearly 18,000 tubes, and the IBM 700 series. This article is about the machine. ... A Colossus Mark II computer. ... ENIAC ENIAC, short for Electronic Numerical Integrator And Computer,[1] was the first large-scale, electronic, digital computer capable of being reprogrammed to solve a full range of computing problems,[2] although earlier computers had been built with some of these properties. ... The IBM 700/7000 series was a series of incompatible large scale (mainframe) computer systems made by IBM through the 1950s and early 1960s. ...


Vacuum tubes are less susceptible than corresponding solid-state components to the electromagnetic pulse effect of nuclear explosions. This property kept them in use for certain military applications long after transistors had replaced them elsewhere. Vacuum tubes are still used for very high-powered applications such as microwave ovens, industrial radio-frequency heating, generating large amounts of RF energy for particle accelerators, and power amplification for broadcasting. Many audiophiles, professional audio engineers, and musicians prefer the tube sound of audio equipment based on vacuum tubes over electronics based on transistors. There are companies which still make specialized audio hardware featuring tube technology. Tubes are still being manufactured today in China (Shuguang Electron Group Co., Tianjin tube factory, Nanjing Sanle Electronics Co., JiangXi Jingguang Electronics Co., Huaguang Electric Power & Electronics Co.), Russia (Reflector/New Sensor Corp., Voskhod-KRLZ, Ryazan LLC. and SED St. Petersburg), USA (Western Electric Inc., Communications & Power Industries Inc. [Eimac], Burle Industries Inc., MPD Components Inc.), France (Thales Electron Devices), Czech Republic (Emission Labs, Tesla Electrontubes s.r.o.), Slovakia (JJ-Electronic) and Serbia (Ei RC). The term electromagnetic pulse (EMP) has the following meanings: electromagnetic radiation from an explosion (especially a nuclear explosion) or an intensely fluctuating magnetic field caused by Compton-recoil electrons and photoelectrons from photons scattered in the materials of the electronic or explosive device or in a surrounding medium. ... It has been suggested that Nuclear explosive be merged into this article or section. ... Microwave oven A microwave oven, or microwave, is a kitchen appliance employing microwave radiation primarily to cook or heat food. ... Atom Smasher redirects here. ... An audiophile, from Latin audire[1] to hear and Greek philos[2] loving, can be generally defined as a person dedicated to achieving high fidelity in the recording and playback of music . ... This article uses the term tube amplifier, also known as a valve amplifier. ... Assorted discrete transistors A transistor is a semiconductor device, commonly used as an amplifier or an electrically controlled switch. ...

Russian 12AX7 tubes inside a modern guitar amplifier.
Russian 12AX7 tubes inside a modern guitar amplifier.

The sound produced by a tube based amplifier with the tubes overloaded (overdriven) is widely used in electric guitar amplification, and has defined the texture of some genres of music such as classic rock and blues. Guitarists often prefer tube amplifiers for the perceived warmth of their tone and the natural compression effect they can apply to an input signal. Image File history File linksMetadata Download high resolution version (1024x676, 105 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Vacuum tube Metadata This file contains additional information, probably added from the digital camera or scanner... Image File history File linksMetadata Download high resolution version (1024x676, 105 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Vacuum tube Metadata This file contains additional information, probably added from the digital camera or scanner... Overdrive in the field of rock music, is a term used for an electric guitar amplifier when turned up, usually deliberately, to the point where distortion (clipping) is clearly audible in the output signal. ... Two different electric guitars. ... An instrument amplifier is an electronic amplifier designed for use with an electric or electronic musical instrument, such as an electric guitar. ...


In 2002, computer motherboard maker AOpen brought back the vacuum tube for modern computer use by releasing the AX4GE Tube-G motherboard. This motherboard uses a Sovtek 6922 vacuum tube (a version of the 6DJ8) as part of AOpen’s TubeSound Technology. AOpen claims that the vacuum tube brings superior sound. AOpen is a major electronics manufacturer that makes computers and parts for computers. ... ECC88, 6922, 6DJ8 and 6N23P The 6DJ8 is a miniature 9-pin medium gain dual triode vacuum tube. ...


Cooling

Like any electronic device, vacuum tubes produce heat while operating. Compared to semiconductor devices, larger tubes operate at higher power levels and hence dissipate more heat. The majority of the heat is dissipated at the anode, though some of the grids can also dissipate power. The tube's heater also contributes to the total (and is a heat source that is absent in semiconductors).


Various methods of cooling are used to remove generated heat. For low-power dissipation devices the heat is radiated from the anode, which often is blackened on the external surface to assist infrared radiation. Natural air circulation or convection is usually required to keep power tubes from overheating. For larger power dissipation, forced-air cooling (fans) may be required. Convection in the most general terms refers to the movement of currents within fluids (i. ...


From the inception of this technology until the 1950s, the dominant approach to cooling low-power tubes remained aimed at avoiding immediate or very short term failures. For noncritical consumer applications, and in absence of technological alternatives, tube failures did not create major problems for equipment manufacturers, as the cost of tube replacements was borne by end users long accustomed to the experience. Some tubes for the US defense market featured a metal casing, as opposed to glass, and an opaque, black finish that facilitated both heat conduction and radiative cooling. In some highly specialized professional applications where replacement was out of the question, such as undersea cable repeaters, no failures were acceptable. Moreover, as vacuum tube based defence systems became increasingly complex and deployed in ever increasing numbers, it became clear that point failures which were individually easy to diagnose and rectify had a devastating effect on the uptime of systems that contained hundreds of tubes. This resulted in both the creation of special long lasting tubes for projects such as Whirlwind and SAGE, and also in special tube shields that aided heat dispersal and could be retrofitted on existing equipment. These shields act by improving heat conduction from the surface of the tube to the shield itself by means of tens of copper tongues in contact with the glass tube, and have an opaque, black outside finish for improved heat radiation. Cross-section of a submarine communications cable. ... Uptime is a measure of the time a computer system has been up and running. ... The Whirlwind computer was developed at the Massachusetts Institute of Technology. ... SAGE Sector Control Room. ...


High-power tubes in older, large transmitters or power amplifiers are liquid cooled, usually with deionised water for heat transfer to an external radiator, similar to the cooling system of an internal combustion engine. Since the anode is usually the cooled element, the anode voltage appears directly on the cooling water surface, thus requiring the water to be an electrical insulator. Otherwise the high voltage can be conducted through the cooling water to the radiator system; hence the need for deionised water. Such systems usually have a built-in water-conductance monitor which will shut down the high-tension supply (often tens of kilovolts) if the conductance becomes too high. Some very high-power transmitters, such as those used in shortwave broadcasting and VLF communications, use pressurized steam for cooling. Modern transmitters using tubes mainly in the PA section are now largely cooled by forced air through a radiator or other heat-sinking device.


Other vacuum tube devices

Many devices were built during the 1920–1960 period using vacuum-tube techniques. Most such tubes were rendered obsolete by semiconductors; some techniques for integrating multiple devices in a single module, sharing the same glass envelope have been discussed above, such as the Loewe 3NF. Vacuum-tube electronic devices still in common use include the magnetron, klystron, photomultiplier, x-ray tube and cathode ray tube. The magnetron is the type of tube used in all microwave ovens. In spite of the advancing state of the art in power semiconductor technology, the vacuum tube still has reliability and cost advantages for high-frequency RF power generation. Photomultipliers are still the most sensitive detectors of light. Many televisions, oscilloscopes and computer monitors still use cathode ray tubes, though flat panel displays are becoming more popular as prices drop. The Loewe 3NF was an early attempt to combine several functions in one Electronic device. ... A cavity magnetron is a high-powered vacuum tube that generates coherent microwaves. ... Reflex klystron Type 2K25 or 723 A/B. The threaded adjustment rod on the right side allows the position of the reflector to be adjusted (by compressing the reflex cavity), and thus the natural resonant frequency of the device. ... Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ... An X-Ray tube is a vacuum tube designed to produce man made X-Ray photons on demand. ... Cathode ray tube employing electromagnetic focus and deflection Cutaway rendering of a color CRT: 1. ... Microwave oven A microwave oven, or microwave, is a kitchen appliance employing microwave radiation primarily to cook or heat food. ... Illustration showing the interior of a cathode-ray tube for use in an oscilloscope. ... Flat panel displays encompass a growing number of technologies enabling video displays that are lighter and much thinner than traditional television and video displays using cathode ray tubes, usually less than 10 cm (4 inches) thick. ...


Many of the better tube radios had so-called "tuning eye" indicator tubes behind their front panels, with just the top of the tube showing. See External Links, below: "Good article about tuning eye tubes". This article describes tubes used in the USA; Europe had tubes that worked on the same general principles, but different-looking.


Secondary emission is the term for what happens when electrons in a vacuum strike certain materials, and the impacts cause electrons to be emitted. For some materials, more electrons are emitted than originally hit the surface. Such devices, called electron multipliers, amplify the current represented by the incoming electrons. Several stages (as many as 15 or so) can be cascaded for high gain, and are essential parts of very sensitive phototubes, usually called photomultipliers or multiplier photoubes. The image orthicon TV studio camera tubes also used multistage photomultipliers. Secondary emission is a phenomenon that occurs in electron tubes where electrons impact an electrode with sufficient energy to knock additional electrons from the surface of that electrode. ...


For decades, electron-tube designers tried to use secondary emission to obtain more amplification in vacuum tubes with hot cathodes, but they suffered from short life because the material used for the secondary-emission electrode (called a dynode) "poisoned" the tube's hot cathode. (For instance, the interesting RCA 1630 secondary-emission tube was marketed, but did not last.) However, eventually, Philips of The Netherlands developed the EFP60 tube that had a satisfactory lifetime, and was used in at least one product, a laboratory pulse generator. However, transistors were rapidly improving, and eclipsed tubes in general.


A variant, called a channel electron multiplier, is simply a curved tube, such as a helix, coated on the inside with material with good secondary emission. One type had a little funnel to capture incoming electrons. The tube was resistive, and its ends were connected to enough voltage to create repeated cascades of electrons.


Tektronix made a high-performance wideband oscilloscope CRT with a channel electron multiplier plate behind the phosphor layer. This plate was a bundled array of a huge number of short individual c.e.m. tubes that accepted a low-current beam and intensified it to provide a display of practical brightness. (The electron optics of the wideband electron gun could not provide enough current to directly excite the phosphor.)


The fluorescent displays commonly used on VCRs and automotive dashboards are actually vacuum tubes, using phosphor-coated anodes to form the display characters, and a heated filamentary cathode as an electron source. These devices are properly called "VFDs", or Vacuum Fluorescent Displays. Because the filaments are in view, they must be operated at temperatures where the filament does not glow visibly. These devices are often found in automotive applications, where their high brightness allows reading the display in daylight. Green screen A phosphor is a substance that exhibits the phenomenon of phosphorescence (sustained glowing after exposure to light or energised particles such as electrons). ... A full view of a typical vacuum fluorescent display used in a videocassette recorder A close-up of the VFD highlighting the multiple filaments, tensioned by the sheet metal springs at the right of the image A vacuum fluorescent display (VFD) is a type of display used commonly on consumer...


Some tubes, like magnetrons, traveling wave tubes, carcinotrons, and klystrons, combine magnetic and electrostatic effects. These are efficient (usually narrow-band) RF producers and still find use in radar, microwave ovens and industrial heating. Traveling-wave tubes (TWTs) are very good amplifiers; they are used in some communications satellites. High-powered klystron amplifier tubes can provide hundreds of kW in the UHF range. A cavity magnetron is a high-powered vacuum tube that generates coherent microwaves. ... A traveling wave tube (TWT) is an electronic device used to produce high-power radio frequency signals. ... A backward wave oscillator (BWO), also called carcinotron or backward wave tube, is a device that is used to generate microwaves and terahertz radiation. ... Reflex klystron Type 2K25 or 723 A/B. The threaded adjustment rod on the right side allows the position of the reflector to be adjusted (by compressing the reflex cavity), and thus the natural resonant frequency of the device. ... For other uses, see Radar (disambiguation). ... Microwave oven A microwave oven, or microwave, is a kitchen appliance employing microwave radiation primarily to cook or heat food. ...


Gyrotrons or vacuum masers, used to generate high-power millimetre band waves, are magnetic vacuum tubes in which a small relativistic effect, due to the high voltage, is used for bunching the electrons. Gyrotrons can generate very high powers (hundreds of kW). Free electron lasers, used to generate high-power coherent light and perhaps even X rays, are highly relativistic vacuum tubes driven by high-energy particle accelerators. Gyrotrons are high powered electron tubes which emit a millimeter wave beam by bunching electrons with cyclotron motion in a strong magnetic field. ... Albert Einsteins theory of relativity is a set of two theories in physics: special relativity and general relativity. ... X-ray free electronic laser schema of operation A free electron laser, or FEL, is a laser that shares the same optical properties as conventional lasers such as emitting a beam consisting of coherent electromagnetic radiation which can reach high power, but which uses some very different operating principles to... For other uses see X-ray (disambiguation). ...


Particle accelerators can be considered vacuum tubes that work backward, the electric fields driving the electrons, or other charged particles. In this respect, a cathode ray tube is a particle accelerator. Atom Smasher redirects here. ...


A tube in which electrons move through a vacuum (or gaseous medium) within a gas-tight envelope is generically called an electron tube.


Some condenser microphone designs use built-in vacuum tube preamplifiers. A microphone with a cord A microphone, sometimes called a mic (pronounced mike), is a device that converts sound into an electrical signal. ... An example of a typical high-end stereo preamplifier. ...

Jolida JD502B, a modern tube integrated amplifier, with preamp tubes in front, power tubes in back.
Jolida JD502B, a modern tube integrated amplifier, with preamp tubes in front, power tubes in back.

As of 2008, scores of small companies are manufacturing audiophile amplifiers and preamps that use vacuum tubes.[5] An integrated amplifier is a box of electrics that enhances sound from your CD player. ... An audiophile, from Latin audire[1] to hear and Greek philos[2] loving, can be generally defined as a person dedicated to achieving high fidelity in the recording and playback of music . ...


Vacuum tube can also mean a tube with a vacuum. It is e.g. used for demonstration of, and experiments with, free-fall. Look up Vacuum in Wiktionary, the free dictionary. ... Free Fall opens with one of the most stunning first paragraphs I have ever, or am ever likely to, read. ...


Field emitter vacuum tubes

In the early years of the 21st century there has been renewed interest in vacuum tubes, this time in the form of integrated circuits. The most common design uses a cold cathode field emitter, with electrons emitted from a number of sharp nano-scale tips formed on the surface of a metal cathode. Integrated circuit of Atmel Diopsis 740 System on Chip showing memory blocks, logic and input/output pads around the periphery Microchips (EPROM memory) with a transparent window, showing the integrated circuit inside. ... This article is about light sources and indicators. ... Field emission, also known as Fowler-Nordheim tunneling, is a form of quantum tunneling in which electrons pass through a barrier in the presence of a high electric field. ...


Their advantages include greatly enhanced robustness combined with the ability to provide high power outputs at low power consumptions. Operating on the same principles as traditional tubes, prototype device cathodes have been constructed with emitter tips formed using nanotubes, and by etching electrodes as hinged flaps (similar to the technology used to create the microscopic mirrors used in Digital Light Processing) that are stood upright by an electrostatic charge. An inorganic nanotube is a cylindrical molecule often composed of metal oxides, and morphologically similar to a carbon nanotube. ... For political parties using this acronym, see Democratic Labour Party. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interactions. ...


Such integrated microtubes may find application in microwave devices including mobile phones, for Bluetooth and Wi-Fi transmission, in radar and for satellite communication. Presently they are being studied for possible application to flat-panel display construction. This article is about the type of Electromagnetic radiation. ... This article is about the electronic protocol. ... Wi-Fi (IPA: ) is the common name for a popular wireless technology used in home networks, mobile phones, video games and more. ... For other uses, see Radar (disambiguation). ... This article is about artificial satellites. ...


See also

Electronics Portal

Image File history File links Nuvola_apps_ksim. ... This is a list of vacuum tubes: // RETMA tube designation 0Z4 Full-Wave Gas Rectifier 2B7 Twin-Diode Remote-Cutoff Pentode 1L6 Pentagrid Converter 5Y3 6AQ5 (EL90) 6AU6A (EF94) 6BQ5 (EL84) 6C19 6CA7 (EL34) 6CL6 Power Pentode 6DA6 (EF89) 6DJ8 (ECC88) 6J5 6L6 (EL37) 6N3P 6SK7 Remote-Cutoff Pentode 6SN7... The All American Five was a mass-produced, superheterodyne radio receiver with five vacuum tubes first designed and produced in the USA in the 1930s. ... Gas filled tubes are arrangements of electrodes in a gas within an insulating, temperature-resistant envelope. ... Irving Langmuir (January 31, 1881 in Brooklyn, New York - August 16, 1957 in Woods Hole, Massachusetts) was an American chemist and physicist. ... The ten digits of a Z560M Nixie tube. ... It has been suggested that this article or section be merged into output device. ... For other uses, see Neon (disambiguation). ... Pneumatic tubes, also known as capsule pipelines or Lamson tubes, are systems in which cylindrical containers are propelled through a network of tubes by compressed air or by vacuum. ... This article uses the term tube amplifier, also known as a valve amplifier. ... A valve amplifier (UK and Aus. ... The Radio Electronics Television Manufacturers Association was formed in 1953, as a result of mergers with other trade standards organisations. ... In Europe, the principal method of numbering vacuum tubes was the nomenclature developed and used by Mullard in the UK and applied Europe-wide thanks to their parentage by Philips who had subsidiaries in Germany (Valvo) and France. ...

Patents

  • U.S. Patent 803,684  - Instrument for converting alternating electric currents into continuous currents (Fleming valve patent)
  • U.S. Patent 841,387  - Device for amplifying feeble electrical currents
  • U.S. Patent 879,532  - De Forest's Audion
  • U.S. Patent 2,141,059  - Television system

Fleming valve schematic from US Patent 803,684. ... This article does not cite any references or sources. ...

Notes

  1. ^ U.S. Patent 307,031 
  2. ^ Robert von Lieben — Patent Nr 179807 Dated November 19, 1906 (PDF). Kaiserliches Patentamt (1906-11-19). Retrieved on 2008-03-30.
  3. ^ U.S. Patent 879,532 
  4. ^ Introduction to Thermionic Valves (Vacuum Tubes), Colin J. Seymour
  5. ^ World Tube Audio Portal.

PDF is an abbreviation with several meanings: Portable Document Format Post-doctoral fellowship Probability density function There also is an electronic design automation company named PDF Solutions. ... Year 1906 (MCMVI) was a common year starting on Monday (link will display full calendar) of the Gregorian calendar (or a common year starting on Sunday of the 13-day-slower Julian calendar). ... is the 323rd day of the year (324th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Common Era (or Anno Domini), in accordance with the Gregorian calendar. ... is the 89th day of the year (90th in leap years) in the Gregorian calendar. ...

References

  • Spangenberg, Karl R. (1948). Vacuum Tubes. McGraw-Hill. LCC TK7872.V3 OCLC 567981. 
  • Millman, J. & Seely, S. Electronics, 2nd ed. McGraw-Hill, 1951.
  • Shiers, George, "The First Electron Tube", Scientific American, March 1969, p. 104.
  • Tyne, Gerald, Saga of The Vacuum Tube, Ziff Publishing, 1943, (reprint 1994 Prompt Publications), pp. 30-83.
  • Stokes, John, 70 Years of Radio Tubes and Valves, Vestal Press, NY, 1982, pp. 3-9.
  • Thrower, Keith, History of The British Radio Valve to 1940, MMA International, 1982, pp 9-13.
  • Eastman, Austin V., Fundamentals of Vacuum Tubes, McGraw-Hill, 1949
  • Philips Technical Library. A range of books published in the UK in the 1940s and 50s by Cleaver Hume Press on all aspects of the design and application of vacuum tubes. They were originally published in Dutch in Holland. French and German editions were probably also published.
  • RCA "Radiotron Designer's Handbook" 1953(4th Edition) Contains very useful chapters on the design and application of receiving tubes.
  • Wireless World. "Radio Designer's Handbook". UK reprint of the above.
  • RCA "Receiving Tube Manual" RC15, RC26 (1947, 1968) Issued every two years, contains details of the technical specs of the tubes that RCA sold at the time.

Library of Congress reading room The Library of Congress Classification (LCC) is a system of library classification developed by the Library of Congress. ... The Online Computer Library Center (OCLC) was founded in 1967 and originally named the Ohio College Library Center. ...

External links

Wikimedia Commons has media related to:
Vacuum tubes


  Results from FactBites:
 
Vacuum tube - Wikipedia, the free encyclopedia (3863 words)
Once the tube envelope is evacuated and sealed, the getter is heated to a high temperature (usually by means of RF induction heating) causing the material to evaporate, adsorbing/reacting with any residual gases and usually leaving a silver-colored metallic deposit on the inside of the envelope of the tube.
Vacuum tubes inherently have higher resistance to the electromagnetic pulse effect of nuclear explosions.
Tubes are also considered by many people in the audiophile, professional audio, and musician communities to have superior audio characteristics over transistor electronics, due to their warmer more natural tone.
  More results at FactBites »

 
 

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